Presently, communication service providers, such as AT&T, offer high-speed Asynchronous Transport Mode (ATM) Virtual Private Network (VPN) service to customers. Each ATM-based VPN customer utilizes one or more Permanent Virtual Circuits (PVCs) to route data among different locations (endpoints), each typically located at a separate edge of an ATM network. In practice, traffic originating at an endpoint passes to an edge device on the ATM network for transmission to the network core, which in turn, transmits such traffic to an edge device serving the destination end point. While the edge devices may run one or more different protocols, including ATM or Frame Relay, the network core typically utilizes the ATM protocol. In this environment, ATM PVCs constitute a point-to-point network topology.
Currently, there exists a large embedded base of Ethernet Local Area Networks (LANs). Advances in Ethernet technology have lead to the development of Metropolitan Area Networks (MANs) that afford access to the Internet and some limited access to VPNs. Ethernet-based MANs offer significant cost advantages on a per port basis, as compared to Frame Relay and ATM networks. Many VPN customers would like the opportunity to use an Ethernet-based MAN to access their ATM-based VPNs but have not had the ability to do so because of interworking issues. The protocol associated with Ethernet is different than that associated with ATM. Ethernet is a broadcast protocol within level 2 (the data link layer) of the well-known 7-layer OSI model, whereas ATM and Frame Relay is a point-to-point circuit-type protocol within level 2. Ethernet is designated as a broadcast protocol within level 2 because information in an Ethernet network travels in both directions and passes by all devices on the path. A device that recognizes the information intended for itself (as opposed to another device) will pull the information from the network.
Thus, in the past, a customer seeking to use an Ethernet-based MAN to route traffic to a VPN served by an ATM network had to worry about both Ethernet and ATM protocols. Interconnecting these two protocols typically required a high level device like a router.
Thus, there is a need for an interworking technique that enables a customer on a first network, such as an Ethernet MAN, for example, to send information to an end point on a second network, such as an endpoint on an ATM network, without any concern as to the protocol of the network serving that endpoint. Furthermore, this technique must be able to interwork between a broadcast domain and a point-to-point circuit-based-domain.